Radiotherapy or surgery of the axilla after a positive sentinel node in breast cancer (EORTC 10981-22023 AMAROS): a randomised, multicentre, open-label, phase 3 non-inferiority trial

For patients with early-stage (T1-2) breast cancer and a positive sentinel node, is axillary radiotherapy a non-inferior alternative to the standard axillary lymph node dissection (ALND) in terms of regional control, while potentially reducing treatment-related morbidity?

The AMAROS trial was a large, multicentre, open-label, phase 3 non-inferiority trial. Researchers randomised 4,806 eligible patients (1:1) to either ALND or axillary radiotherapy. The primary endpoint was the 5-year axillary recurrence rate. Secondary endpoints included disease-free survival, overall survival, shoulder mobility, and quality of life (QoL), with a specific focus on the incidence of lymphoedema.

Both treatment arms demonstrated excellent and comparable regional control. The 5-year axillary recurrence rate was 0.43% for the ALND group and 1.19% for the radiotherapy group. There were no significant differences in disease-free or overall survival between the two groups. However, the study found a clear clinical advantage for radiotherapy regarding morbidity: patients treated with ALND experienced significantly higher rates of lymphoedema at 1, 3, and 5 years compared to those who received radiotherapy. Despite these differences in physical morbidity, there were no statistically significant differences in patient-reported quality of life scores between the two groups.

These results provide strong evidence that axillary radiotherapy is a viable, less morbid alternative to ALND for patients with early-stage breast cancer who have a positive sentinel node. While previous trials (such as ACOSOG Z0011) established that some patients can avoid axillary treatment altogether, the AMAROS trial offers a clear, evidence-based option for those who still require regional axillary intervention, allowing clinicians to minimize long-term side effects like lymphoedema without compromising oncological safety.